The World Mill is a mytheme suggested as recurring in Indo-European and other mythologies. It involves the analogy of the cosmos or firmament and a rotating millstone. The mytheme was extensively explored in Viktor Rydberg's 1886 Investigations into Germanic Mythology, who provides both ancient Scandinavian and Indian examples. Donald Mackenzie described the World Mill’s relationship to the sacred spiral and the revolution of the starry heavens, providing analogs in Chinese, Egyptian, Babylonian, and AmerInd folklore, before concluding "that the idea of the World Mill originated as a result of the observation of the seasonal revolutions of the constellation of the 'Great Bear'."